Universal Serial bus charger for a mobile device

ABSTRACT

In accordance with the teachings described herein, systems and methods are provided for charging a rechargeable power source in a mobile device through a USB port. A power converter may be used to receive an input voltage from an external power source and generate a charger output having a regulated voltage. A signal generator may be used to generate a charger configuration signal having pre-selected waveform characteristics that are selected to identify operating characteristics of the charging apparatus. A USB connector may be used for coupling the charger output and charger configuration signal to the USB port on the mobile device. The USB connector may include a voltage bus (Vbus) contact coupled to the charger output, a positive data (D+) contact coupled to the charger configuration signal, and a negative data (D−) contact coupled to the charger configuration signal. The charger configuration signal may be transmitted simultaneously to the D+ and D− contacts, such that the D+ and D− contacts are continuously either both in a logic high state or both in a logic low state. The mobile device may be configured to identify the operating characteristics of the charging apparatus from the waveform characteristics of the charger configuration signal and to apply the charger output to recharge the rechargeable power source.

CROSS-REFERENCE

[0001] This application claims the benefit of British Application No.0313485.5 filed on Jun. 11, 2003 and entitled “Universal Serial BusCharger For A Mobile Device,” the entire disclosure of which isincorporated herein by reference.

FIELD

[0002] The technology described in this patent document relatesgenerally to the field of power adapters. More particularly, this patentdocument describes a Universal Serial Bus (USB) charger that isparticular well-suited for supplying power to a mobile device, such as awireless two-way messaging device, a cellular telephone, a personaldigital assistant (PDA), or other hand-held device having a rechargeablepower source.

BACKGROUND

[0003] Providing an external source of power to a mobile device, such asa personal digital assistant (“PDA”), wireless two-way messaging device,cellular phone, and others, requires design considerations with respectto both the mobile device and the power source. With regard to themobile device, most mobile devices provide a distinct power interfacefor receiving power from a power source, for instance to recharge abattery, and a separate data interface for communicating. For example,many mobile devices use USB (Universal Serial Bus) interfaces forcommunicating and use a separate power interface, such as a barrelconnector, for receiving power.

SUMMARY

[0004] In accordance with the teachings described herein, systems andmethods are provided for charging a rechargeable power source in amobile device through a USB port. A power converter may be used toreceive an input voltage from an external power source and generate acharger output having a regulated voltage. A signal generator may beused to generate a charger configuration signal having pre-selectedwaveform characteristics that are selected to identify operatingcharacteristics of the charging apparatus. A USB connector may be usedfor coupling the charger output and charger configuration signal to theUSB port on the mobile device. The USB connector may include a voltagebus (Vbus) contact coupled to the charger output, a positive data (D+)contact coupled to the charger configuration signal, and a negative data(D−) contact coupled to the charger configuration signal. The chargerconfiguration signal may be transmitted simultaneously to the D+ and D−contacts, such that the D+ and D− contacts are continuously either bothin a logic high state or both in a logic low state. The mobile devicemay be configured to identify the operating characteristics of thecharging apparatus from the waveform characteristics of the chargerconfiguration signal and to apply the charger output to recharge therechargeable power source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a block diagram of an example USB charger for charging arechargeable power source in a mobile device;

[0006]FIG. 2 illustrates an example charger configuration signaltransmitted simultaneously on the USB D+ and D− lines shown in FIG. 1;

[0007]FIG. 3 is a circuit diagram of an example signal generator for theUSB charger of FIG. 1;

[0008]FIG. 4 is a block diagram of an example mobile device for use witha USB charger;

[0009]FIG. 5 is a flow diagram illustrating an example method forcharging a rechargeable power source via a USB port in a mobile device;and

[0010]FIG. 6 is a block diagram of another example USB charger forcharging a rechargeable power source in a mobile device.

DETAILED DESCRIPTION

[0011] With reference now to the drawing figures, FIG. 1 is a blockdiagram 100 of an example USB charger 110 for charging a rechargeablepower source in a mobile device 132. The USB charger 110 includes apower converter 112, a signal generator 114, and a USB connector 116.Also illustrated are an external power source 130 and the mobile device132.

[0012] The power converter 112 is configured to receive an input voltagefrom the external power source 130 and generate a charger output 113having a regulated voltage. The USB charger 110 may be configured tooperate with either an AC external power source 130, such as aconventional household power outlet, or a DC external power source 130,such as the power socket in an automobile. In the case of an AC powersource 130, the power converter 112 may include an AC/DC converter thatconverts the AC input voltage of the external power source 130 into aregulated DC voltage at the charger output 113. If the external powersource 130 is a DC power source, then the power converter 112 mayinclude a DC/DC converter to generate the regulated DC voltage expectedat the charger output 113.

[0013] The signal generator 114 is configured to generate a chargerconfiguration signal 115, which is a periodic signal having pre-selectedwaveform characteristics that are selected to identify operatingcharacteristics of the USB charger 110. The pre-selected waveformcharacteristics may, for example, include a constant operating frequencyand duty-cycle. The operating characteristics identified by thepre-selected waveform characteristics of the charger configurationsignal 115 may include the values of the regulated voltage and maximumcurrent capability of the charger output 113, the model number of thecharger, and/or other information relevant to the operation of the USBcharger 110. Example waveform characteristics of the chargerconfiguration signal 115 are described in more detail below withreference to FIG. 2.

[0014] The USB connector 116 is preferably a standard 4 pin USBconnector having a voltage bus (Vbus) contact 118, a positive data (D+)contact 120, a negative data (D−) 122 contact, and a ground contact 124,as described in the Universal Serial Bus Specification, Revision 2.0,published Apr. 27, 2000. The Vbus contact 118 is coupled to the chargeroutput 113 and both the D+ and D− contacts 120, 122 are coupled to thecharger configuration signal 115. The ground contact 124 is coupled to aground potential from the power converter 112, but could alternativelybe coupled to another grounding source.

[0015] The mobile device 132 includes a USB port 134 that is coupled tothe USB connector 116 of the USB charger 110. The mobile device 132 isconfigured to identify the operating characteristics of the chargingapparatus 110 from the waveform characteristics of the chargerconfiguration signal 115 and to apply the charger output 113 to rechargea rechargeable power source in the mobile device 132. The rechargeablepower source in the mobile device 132 may, for example, be arechargeable Lithium-Ion battery, or some other type of rechargeablebattery. The USB port 134 on the mobile device 132 may be connected tothe USB connector 116 of the USB charger 110 using a docking cradle, astandard USB cable, or by other suitable means. A detailed descriptionof an example mobile device 132 is provided below with reference to FIG.4.

[0016] In operation, the USB charger 110 transmits the chargerconfiguration signal 113 to the mobile device 132 simultaneously on boththe USB D+ and D− lines 120, 122, causing the D+ and D− lines to becontinuously either both in a logic high state or both in a logic lowstate. In accordance with the USB Specification, a logic high state onboth the D+ and D− lines signals an “Illegal” state, and a logic lowstate on both the D+ and D− lines signals a “Reset” state. Accordingly,simultaneous logic high or logic low states on the D+ and D− lines arenot used during the transmission of data between a USB host and a USBperipheral device. Therefore, the mobile device 132 may be configured torecognize the presence of a charger configuration signal 113 transmittedsimultaneously on the USB D+ and D− lines 120, 122, without interferingwith the mobile device's ability to communication with a typical USBhost device. For example, when the mobile device 132 detects power onthe Vbus line 118, it may first attempt to establish a connection with aUSB host using a standard USB enumeration process. If a USB host is notdetected, then the mobile device 132 may monitor the D+ and D− lines120, 122 for the presence of a charger configuration signal 113.

[0017] Once the mobile device 132 detects a charger configuration signal113 on the USB D+ and D− lines 120, 122, the device 132 analyzes thewaveform characteristics of the signal 113 to determine the operatingcharacteristics of the USB charger 110. For instance, the mobile device132 may determine the maximum current capability of the charger 110 fromthe charger configuration signal 113. The mobile device 132 may thendraw power from the Vbus line 118 up to the maximum available current inorder to charge its rechargeable power supply.

[0018]FIG. 2 illustrates an example charger configuration signal 115transmitted simultaneously on the USB D+ and D− lines 120, 122, as shownin FIG. 1. FIG. 2 includes two graphs 200, 210, plotting the chargerconfiguration signal 115 as a function of time for the D+ and D− lines,respectively. The illustrated charger configuration signal 115 is aperiodic digital signal having a constant frequency (1/T) and a constantduty-cycle (T_(H)/T). As noted above, the frequency (1/T) and duty-cycle(T_(H)/T) of the signal 115 may be selected to identify certainoperating characteristics of the USB charger 110. For example, thefrequency (1/T) may identify the model and/or manufacturer of thecharger 110, and the duty-cycle (T_(H)/T) may identify certain operatingcharacteristics associated with the particular model charger 110, suchas the voltage and/or maximum available current of the charger output113.

[0019]FIG. 3 is a circuit diagram of an example signal generator 114 forthe USB charger 110 of FIG. 1. The example signal generator 114 includesa digital timer 310, a switching circuit 312, and an RC circuit 314-316.In operation, the frequency and duty-cycle of the charger configurationsignal 115 may be adjusted by selecting the resistor and capacitorvalues in the RC circuit 314-316.

[0020] The digital timer 310 may, for example, be a standard timer IC,such as an LM555 timer. The timer 310 generates a timer output signal318 that may be tuned by varying the resistor and capacitor values inthe RC circuit 314-316, which is coupled between the discharge (DIS) andthreshold (THR) inputs of the timer 310. The timer output signal 318 iscoupled as the inputs of two transistor pairs 320, 322 and 324, 326 inthe switching circuit 312, which adjusts the peak voltage and impedanceat the D+ and D− outputs 120, 122 to simulate those of a typical USBhost. The values of the resistors (R1-R6) in the switching circuit 312are chosen to set the output voltage and impedance at the D+ and D−outputs 120, 122. For example, the switching circuit 312 may regulatethe voltage at the D+ and D− outputs 120, 122 to a peak voltage rangebetween 3.0 to 3.6 volts and provide an output resistance between 14.25Kand 24.8K Ohms, as required of USB hosts under the USB Specification.

[0021]FIG. 4 is a block diagram of an exemplary mobile device 132 thatincludes a system for drawing power through a USB interface 412 from aUSB charger 110. The mobile device 132 includes the USB interface 412, aUSB controller 414, a charging subsystem 416, a rechargeable battery418, and a processing device 420.

[0022] The USB interface 412 is coupled to the USB charger 110, asdescribed above. The USB interface 412 includes a Vbus power line 424that is coupled to the charging subsystem 416, and USB data lines 426which are coupled to the USB controller 414. Operationally, the USBinterface 412 is used by the mobile device 132 to provide power to thecharging subsystem 416, and may also be used to communicate data betweena USB host or hub (not shown) and the USB controller 414.

[0023] The charging subsystem 416 provides power to the mobile device132, either from the rechargeable battery 418 or from the Vbus powerline 424, and charges the rechargeable battery 418 from the Vbus powerline 424. The USB controller 414 monitors the USB data lines 426, andcontrols data communication between the processing device 420 and a USBhost. In addition, the USB controller 414 detects the presence of a USBcharger 110 by identifying a charger configuration signal 115 on the D+and D− lines, and determines the operational characteristics of thecharger from the waveform characteristics of the charger configurationsignal 115, as described above. For example, the mobile device 400 maymaintain a look-up table used by the USB controller 414 to matchidentified waveform characteristics with corresponding chargeroperational characteristics, such as a maximum available current.

[0024] Upon detection of a charger configuration signal 114 by the USBcontroller 414, the identified operational characteristics of the USBcharger 110 are provided to the charging subsystem 416, which instructsthe USB interface 412 to begin drawing power from the Vbus line tocharge the rechargeable battery 418. The charging subsystem 416 may, forexample, instruct the USB interface 412 to draw power from the Vbus lineup to a maximum available charge current identified from the chargerconfiguration signal 114.

[0025] In addition to the subsystems and components described above, themobile device 132 also may include a communications subsystem 428, ashort-range communications subsystem 430, input/output devices 432-440,memory devices 442, 444, and various other device subsystems 446.

[0026] The processing device 420 controls the overall operation of themobile device 132. Operating system software executed by the processingdevice 420 is preferably stored in a persistent store such as a flashmemory 444, but may also be stored in other types of memory devices,such as a read only memory (ROM) or similar storage element. Inaddition, operating system software, specific device applications, orparts thereof, may be temporarily loaded into a volatile store, such asa random access memory (RAM) 442. Communication signals received by themobile device 132 may also be stored to RAM 442.

[0027] The processing device 420, in addition to its operating systemfunctions, enables execution of software applications on the device 132.A predetermined set of applications that control basic deviceoperations, such as data and voice communications, may be installed onthe device 132 during manufacture. In addition, a personal informationmanager (PIM) application may be installed during manufacture. The PIMis preferably capable of organizing and managing data items, such ase-mail, calendar events, voice mails, appointments, and task items. ThePIM application is also preferably capable of sending and receiving dataitems via the wireless network 460. Preferably, the PIM data items areseamlessly integrated, synchronized and updated via the wireless network460 with the device user's corresponding data items stored or associatedwith a host computer system. An example system and method foraccomplishing these steps is disclosed in “System And Method For PushingInformation From A Host System To A Mobile Device Having A SharedElectronic Address,” U.S. Pat. No. 6,219,694, which is owned by theassignee of the present application, and which is hereby incorporatedinto the present application by reference.

[0028] Communication functions, including data and voice communications,are performed through the communication subsystem 428, and possiblythrough the short-range communications subsystem 430. If the mobiledevice 132 is enabled for two-way communications, then the communicationsubsystem 428 includes a receiver 448, a transmitter 450, and aprocessing module 458, such as a digital signal processor (DSP). Inaddition, the communication subsystem 428, configured as a two-waycommunications device, includes one or more, preferably embedded orinternal, antenna elements 452, 454, and local oscillators (LOs) 456.The specific design and implementation of the communication subsystem428 is dependent upon the communication network 460 in which the mobiledevice 132 is intended to operate. For example, a device 132 destinedfor a North American market may include a communication subsystem 428designed to operate within the Mobitex™ mobile communication system orDataTAC™ mobile communication system, whereas a device 132 intended foruse in Europe may incorporate a General Packet Radio Service (GPRS)communication subsystem.

[0029] Network access requirements vary depending upon the type ofcommunication system 460. For example, in the Mobitex™ and DataTAC™networks, mobile devices are registered on the network using a uniquepersonal identification number or PIN associated with each device. InGPRS networks, however, network access is associated with a subscriberor user of a device. A GPRS device therefore requires a subscriberidentity module, commonly referred to as a SIM card, in order to operateon a GPRS network.

[0030] When required network registration or activation procedures havebeen completed, the mobile device 132 may send and receive communicationsignals over the communication network 460. Signals received by theantenna 452 through the communication network 460 are input to thereceiver 448, which may perform such common receiver functions as signalamplification, frequency down conversion, filtering, channel selection,and analog-to-digital conversion. Analog-to-digital conversion of thereceived signal allows the DSP to perform more complex communicationfunctions, such as demodulation and decoding. In a similar manner,signals to be transmitted are processed by the DSP 458, and are theinput to the transmitter 450 for digital-to-analog conversion, frequencyup-conversion, filtering, amplification and transmission over thecommunication network 460 via the antenna 454.

[0031] In addition to processing communication signals, the DSP 458provides for receiver 448 and transmitter 450 control. For example,gains applied to communication signals in the receiver 448 andtransmitter 450 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 458.

[0032] In a data communication mode, a received signal, such as a textmessage or web page download, is processed by the communicationsubsystem 428 and input to the processing device 420. The receivedsignal is then further processed by the processing device 420 for outputto a display 432, or alternatively to some other auxiliary I/O device440. A device user may also compose data items, such as e-mail messages,using a keyboard 434, such as a QWERTY-style keyboard, and/or some otherauxiliary I/O device 440, such as a touchpad, a rocker switch, athumb-wheel, or some other type of input device. The composed data itemsmay then be transmitted over the communication network 460 via thecommunication subsystem 428.

[0033] In a voice communication mode, overall operation of the device132 is substantially similar to data communication mode, except thatreceived signals are output to a speaker 436, and signals fortransmission are generated by a microphone 438. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 132. In addition, the display 432 mayalso be utilized in voice communication mode, for example to display theidentity of a calling party, the duration of a voice call, or othervoice call related information.

[0034] The short-range communications subsystem 430 enablescommunication between the mobile device 132 and other proximate systemsor devices, which need not necessarily be similar devices. For example,the short-range communications subsystem 430 may include an infrareddevice and associated circuits and components, or a Bluetooth™communication module to provide for communication with similarly-enabledsystems and devices.

[0035]FIG. 5 is a flow diagram illustrating an example method 500 forcharging a rechargeable power source via a USB port in a mobile device.At step 510, an unknown device is connected to the USB port on themobile device. At step 512, the mobile device attempts to signal theunknown device as a USB host. If the unknown device is a USB host, thena successful USB enumeration occurs at step 614, and the mobile deviceestablishes communication with the USB host at step 516. If the unknowndevice is not a USB host, however, then a USB enumeration will not beinitiated at step 514, and the mobile device monitors the D+ and D−lines for data traffic at step 618. If the unknown device is a USBcharger, as described above, then a charger configuration signal isdetected on the D+ and D− lines by the mobile device at step 520. Themaximum available charger current of the USB charger is determined fromthe charger configuration signal, and a charge current is setaccordingly at step 522. Then, at step 524, the mobile device drawspower from the USB charger via the Vbus line up to the maximum availablecurrent.

[0036] This written description uses examples to disclose the invention,including the best mode, and also to enable a person skilled in the artto make and use the invention. The patentable scope of the invention mayinclude other examples that occur to those skilled in the art. Forexample, FIG. 6 is a block diagram 600 of another example USB charger605 for charging a rechargeable power source in a mobile device 132.This example USB charger 605 is similar to the USB charger 110 of FIG.1, with the addition of a modulator 610 coupled between the signalgenerator 114 and the D+ and D− contacts 120, 122. In this embodiment,the frequency and duty cycle of the periodic output 115 from the signalgenerator 114 may be modulated by the modulator 610 in order to generatea modulated charger configuration signal 611 on the D+ and D− lines 120,122. In this manner, additional information regarding the USB charger605 may be encoded into the charger configuration signal 611 andtransmitted to the mobile device 132.

1. A charging apparatus for charging a rechargeable power source in amobile device through a Universal Serial Bus (USB) port, comprising: apower converter configured to receive an input voltage from an externalpower source and generate a charger output having a regulated voltage; asignal generator configured to generate a charger configuration signalhaving a pre-selected frequency and duty-cycle, wherein the frequencyand duty-cycle of the charger configuration signal are selected toidentify operating characteristics of the charging apparatus, includingat least the values of the regulated voltage an a maximum currentcapability of the charger output; and a USB connector for coupling thecharger output and the charger configuration signal to the USB port ofthe mobile device, the USB connector having a voltage bus (Vbus) contactcoupled to the charger output, a positive data (D+) contact coupled tothe charger configuration signal, and a negative data (D−) contactcoupled to the charger configuration signal, the charger configurationsignal being transmitted simultaneously to the D+ and D− contacts, suchthat the D+ and D− contacts are continuously either both in a logic highstate or both in a logic low state; wherein the mobile device isconfigured to identify the operating characteristics of the chargingapparatus from the frequency and duty-cycle of the charger configurationsignal and apply the charger output to recharge the rechargeable powersource.
 2. The charging apparatus of claim 1, wherein the operatingcharacteristics identified by the charger configuration signal include amodel number for the charging apparatus.
 3. The charging apparatus ofclaim 1, wherein the pre-selected frequency of the charger configurationsignal is a constant frequency that is pre-selected to identify a modelof the charging apparatus.
 4. The charging apparatus of claim 1, whereinthe pre-selected duty-cycle of the charger configuration signal is aconstant duty-cycle that is pre-selected to identify the values of theregulated voltage and maximum current capability of the charger output.5. The charging apparatus of claim 1, wherein the external power sourceis a household AC power outlet, and wherein the power converterfunctions as an AC to DC converter.
 6. The charging apparatus of claim1, wherein the external power source is a DC power source.
 7. Thecharging apparatus of claim 1, wherein the signal generator includes adigital timing circuit that is configured to generate the chargerconfiguration signal.
 8. The charging apparatus of claim 7, wherein thedigital timing circuit includes: a digital timer that is configured togenerate an output signal having a constant frequency and a constantduty-cycle; and a switching circuit coupled between the output signal ofthe digital timer and the D+ and D− contacts of the USB connector, theswitching circuit being configured to regulate the peak voltage of theoutput signal to generate the charger configuration signal.
 9. Thecharging apparatus of claim 8, wherein the switching circuit isconfigured to provide a pre-selected resistance.
 10. The chargingapparatus of claim 1, wherein the signal generator includes an analogtiming circuit that is configured to generate the charger configurationsignal.
 11. A method of charging a rechargeable power source in a mobiledevice, comprising the steps of: generating a charger output having aregulated voltage and a maximum current capacity; generating a chargerconfiguration signal having pre-selected waveform characteristics, thewaveform characteristics including a pre-selected duty-cycle thatidentifies values of the regulated voltage and the maximum currentcapacity of the charger output; and coupling the charger output andcharger configuration signal to the mobile device via a Universal SerialBus (USB) port on the mobile device, the charger configuration signalbeing coupled to both a positive data (D+) contact and a negative data(D−) contact of the USB port and the regulated voltage being coupled toa voltage bus (Vbus) contact of the USB port; wherein the chargerconfiguration signal is transmitted simultaneously to the D+ and D−contacts of the USB port, such that the D+ and D− contacts arecontinuously either both in a logic high state or both in a logic lowstate; wherein the mobile device is configured to identify the values ofthe regulated voltage and maximum current capacity of the charger outputfrom the pre-selected duty-cycle of the charger configuration signal andto apply the charger output to recharge the rechargeable power source.12. The method of claim 11, wherein the pre-selected waveformcharacteristics include a pre-selected frequency that identifies a modelof a charging apparatus.
 13. A method for charging a rechargeable powersource in a mobile device, comprising: detecting an electricalconnection between a Universal Serial Bus (USB) port on the device andan external device; attempting to initiate a USB enumeration procedurewith the external device; if an enumeration acknowledgement signal isnot received from the external device, then monitoring a positive data(D+) contact and a negative data (D−) contact of the USB port for acharger configuration signal, the charger configuration signal beingtransmitted simultaneously on the D+ and D− contacts of the USB portsuch that the charger configuration signal causes the D+ and D− contactsto be continuously either both in a logic high state or both in a logiclow state; and if a charger configuration signal is detected, thendetermining a regulated voltage value and a maximum current value forthe external device from waveform characteristics of the chargerconfiguration signal and configuring the mobile device using theregulated voltage value and the maximum current value to charge therechargeable power source from the external device.
 14. The method ofclaim 13, wherein the waveform characteristics of the chargerconfiguration signal include a constant duty-cycle that is pre-selectedto identify the regulated voltage value and the maximum current value.15. The method of claim 13, further comprising: determining a model typeof the external device from the waveform characteristic of the chargerconfiguration signal and using the model type to configure the mobiledevice to charge the rechargeable power source from the external device.16. The method of claim 15, wherein the waveform characteristics of thecharger configuration signal include a constant frequency that ispre-selected to identify the model type.